Studies on the origin of false positive reactions to the scro-diagnosis for contagious bovine pleurop­neumonia

Abstract

Four groups of cattle were experimentally immunised by four myco­ plasma species of « mycoides-like » group, Mycoplasma (M)  caprico­ lum, M. mycoides subsp.  mycoides (LC),  M.  mycoides subsp.  capri and M. species group 7 of LEACH (PGS0). They were then  bled  weekly during 2 months to establish antibodies kinetics against homologous and heterologous antigens. The standard method of complement fixation test (CFT) used in Europe and a new ELISA test for diagnosis of contagions bovine pleuropneumonia  were  performed in comparison with passive haemagglutination test (PHA) against antigens used for experimental immunisation. Cross reactions obtained are rather equal to the degree of similitude between these mycoplasma species. With CFT-cross reactions are transitory and occur only while homologous titers are very high, particularly with «  PGS0 »  and  the two caprine mycoides strains. ELISA results using a  threshold  of positivity of optical density of 0.20, were similar to  that obtained  with CFT except ELISA specificity is not so different from CFT one. This experimental model could explain some natural situations.